This invention relates to apparatus and methods for manufacturing improved thin-film magnetic recording transducers, commonly referred to as recording transducers. More specifically, it relates to a focused particle beam system for milling a portion of a pole-tip assembly of the recording transducer without irradiating a sensitive structure, e.g. a read head, of the recording transducer.
Thin-film magnetic recording transducers have gained wide acceptance in the data storage industry. A recording transducer includes a write head and a read head. The recording transducer has an air bearing surface that passes adjacent to a recording medium, such as a magnetic disk. The portions of the recording transducer, including portions of the write head and of the read head, that are proximate to the air bearing surface form a small, precisely shaped pole-tip assembly. The size and shape of the pole-tip assembly, which include features on the order of one-half a micron, in part determine the magnetic field pattern produced by the recording transducer. This magnetic field pattern effects how narrowly the recording transducer can record data tracks on the magnetic media of magnetic memory storage devices, such as computer hard disks, and digital data tape drives.
Thinner data tracks allow a storage device to store more data tracks per area of media and therefore more data per device. Accordingly, precisely forming the pole-tip assembly of the recording transducer results in an increase in the total data storage capacity of a magnetic memory device. Manufacturers seek to form the geometry of a pole-tip assembly with high precision, and consequently achieve pole-tip assemblies capable of providing magnetic field patterns suitable for writing narrow tracks of recorded data.
Manufacturers presently fabricate multiple recording transducers from a single multi-layer device, and endeavor to form the precise desired shape of the pole-tip assembly of a recording transducer by employing lithographic techniques in fabricating the multi-layer device. Typically, lithographic techniques deposit alternating layers of conductive and insulating materials onto a substrate by an evaporation, sputtering, plating, or other deposition technique that provides precise control of the deposition thicknesses. Chemical etching, reactive ion etching (RIE), or other techniques shape and form the deposited layers into a pole-tip assembly having the desired geometry. Thus, a multi-layer lithographicaly fabricated device can form a plurality of recording transducers having pole-tip assemblies.
Although existing lithographic techniques work sufficiently well to provide pole-tip assemblies having feature sizes suitable for current data storage capacity, these lithographic techniques are limited as to the small feature sizes that they can produce. For example, present photolithographic techniques require precise application of photoresist layers. Commonly, the photoresist layer is applied to produce a topology that includes voids having aspect ratios of 10:1 or larger. Such topologies are difficult to achieve reliably, at the desired small sizes, using such a photoresist technique.
Thus, these lithographic techniques are poorly suited for achieving a high yield of precisely formed, ultra-small, pole-tip assemblies. In the interest of increased storage density, manufacturers decrease the dimensions of a desired pole-tip assembly. As the dimensions of the desired pole-tip assembly decrease, manufacturers who use existing lithographic techniques experience yield loss. In other words, even if manufacturers using existing lithographic techniques are successful in achieving a desired pole-tip assembly configuration, they generally achieve that desired configuration with a low yield.
The kinds of defects that occur during the manufacturing process are difficult to predict and vary widely. Accordingly, the application of a universal photoresist pattern to the surface of a pole-tip assembly is a generalized solution that often is ill suited to the actual manufacturing defect of any one recording transducer. Therefore, current techniques for producing a magnetic recording transducer have several serious limitations with respect to control of pole-tip assembly geometry.
Consequently, higher density data storage devices can require micromachining of the recording transducer used with the devices. Manufacturers can micromachine the recording transducer while it is contained in a multi-layer device. Prior to micromachining, a multi-layer device is lithographically fabricated. Once the multi-layer device is fabricated, it is cleaved at a selected location and the cleaved surface is polished to expose at least one recording transducer pole-tip assembly formed by the multi-layer device.
The micromachining of a recording transducer can require accurate shaping of a write head. However, the read head can employ a sensitive structure such as a Magneto-Resistive Stripe (MRS). A MRS can suffer damage as a result of irradiation by a focused ion beam (FIB). For background information on the design and function of a MRS and an inductive write head, see the text xe2x80x9cMagneto-Resistive Heads, Fundamentals and Applicationsxe2x80x9d by John C. Mallinson (Academic Press, Inc., San Diego 1996), incorporated herein by reference. It is important to note that the MRS and the write head can each have sublayers. An MRS can include thin-film sublayers, each five to six angstroms thick. The properties of a read head, including a MRS, can be altered during irradiation by a focused ion beam (FIB). Thus, there is a need for focused ion beam systems and methods that locate and accurately shape a write head without irradiating a read head of a pole-tip assembly of a thin-film magnetic recording transducer.
Accordingly, it is an object of the present invention to provide apparatus and methods for manufacturing improved thin-film magnetic recording transducers using a focused particle beam.
It is a further object of the present invention to precisely form the pole-tip assembly of a magnetic recording transducer without irradiating a sensitive structure, e.g., a read head, in the recording transducer.
Other objects of the invention will in part be obvious and will in part appear hereinafter.
The invention is described herein in connection with certain embodiments; however, it will be clear to those skilled in the art of magnetic recording transducer manufacture that various modifications, additions and subtractions can be made to the described embodiments without departing from the spirit or scope of the invention.
The present invention provides apparatus and methods for precisely shaping a pole-tip assembly of a magnetic recording transducer without irradiating a sensitive structure, e.g., a read head in the recording transducer. An apparatus for shaping a pole-tip assembly of a recording transducer with a focused particle beam, according to one embodiment of the invention, includes a platform for receiving a multi-layer device including the recording transducer and for disposing the multi-layer device for interaction with the focused particle beam. The multi-layer device has a first layer including a first structural element, a second layer including a second structural element, and a shielding layer including a shielding element. The first and second structural elements can be a read head and a write head, respectively. The shielding element is located between the first structural element and the second structural element. The structural elements and the shielding element intersect a geometrical surface that extends transversely to the first, second, and shielding layers, so that imaging at least a portion of the shielding element, at the geometrical surface, provides information that facilitates imaging the second structural element without imaging the first structural element.
The apparatus has an element for scanning the focused particle beam over the geometrical surface at a selected first section that includes at least a portion of the shielding element and that does not include the first structural element. The system can select which section of the multi-layer device surface to image by methods, such as an optical microscope registration technique, that are known in the art. The apparatus has an element for generating a first image signal representative of the portion of the shielding element. The first image signal results from interaction of the focused particle beam with the portion of the shielding element. The apparatus has an element for analyzing the first image signal representative of the portion of the shielding element to determine the location of the portion of the shielding element.
The apparatus has an element for directing the focused particle beam, in response to the determined location of the portion of the shielding element, to interact with the second structural element without substantially interacting with the first structural element. The apparatus has an element for generating a second image signal responsive to interaction of the focused particle beam with the second structural element. In addition, the apparatus has a processor element, responsive to the second image signal, for generating a milling signal. The milling signal represents an instruction for applying the focused particle beam to a selected portion of the second structural element for milling the selected portion of the second structural element.
One version of a method according to the present invention employs a focused particle beam to shape a pole-tip assembly of a recording transducer. The method disposes a multi-layer device on a platform for contact with the particle beam. The multi-layer device forms at least one recording transducer. As noted above, the multi-layer device has a first layer including a first structural element, a second layer including a second structural element, and a shielding layer including a shielding element located between the first structural element and the second structural element. The structural elements and the shielding element intersect a geometrical surface that extends transversely to the first, second, and shielding layers, so that imaging at least a portion of the shielding element, at the geometrical surface, provides information to facilitate imaging the second structural element without imaging the first structural element.
The system scans the focused particle beam over the geometrical surface at a selected first section that includes at least a portion of the shielding element and that does not include the first structural element. The system generates a first image signal representative of the portion of the shielding element. The first image signal results from interaction of the focused particle beam with the portion of the shielding element. The system analyzes the first image signal representative of the portion of the shielding element to determine the location of the portion of the shielding element.
The system directs, responsive to the determined location of the portion of the shielding element, the focused particle beam to interact with the second structural element without requiring interaction with the first structural element. The system generates a second image signal responsive to interaction of the focused particle beam with the second structural element. Then, the system generates, responsive to the second image signal, a milling signal. The milling signal represents an instruction for applying the focused particle beam to a selected portion of the second structural element for shaping the pole-tip assembly by milling the selected portion of the second structural element.
According to further features of the invention, the system provides a charge neutralization element for neutralizing charge on the recording transducer.
The scanning of the focused particle beam includes scanning the focused particle beam over the geometrical surface at a selected section that includes the portion of the shielding element closest to the second structural element
The generation of a second image signal includes the generation, responsive to the second image signal, of a coordinate signal. The coordinate signal represents an instruction for applying the focused particle beam to a selected portion of the second structural element for shaping the pole-tip assembly by milling the selected portion of the second structural element.
The generation of a coordinate signal includes the detection of an edge of the second structural element and generates an edge signal The edge signal represents a location of the edge of the second structural element relative to the focused particle beam.
The generation of a milling signal includes generating, as a function of the second image signal. a presentation signal. The presentation signal represents a pattern presentation of the second structural element. The generation of a milling signal can further include comparing the presentation signal to a pattern signal representative of a select second structural element topography. The generation of a milling signal can include comparing the presentation signal to a plurality of pattern signals and selecting one of the pattern signals as a function of the comparison.
The comparison of the presentation signal to the pattern includes the determination of an etching pattern signal representative of one or more areas to etch from the second structural element to conform the second structural element substantially to the select second structural element topography.
The determination of an etching pattern signal includes the determination of a minimum etching-time signal. The etching-time signal represents a minimum length of time to apply a milling pattern in order to conform the second structural element substantially to the select second structural element topography. The determination of an etching pattern signal can further include the determination a minimum etching-area signal. The minimum etching-area signal represents a milling pattern having a minimum area to be removed for conforming the second structural element substantially to the select second structural element topography.
The generation of a milling signal can further include the generation of a representative instruction signal for deflecting said particle beam to a desired location. The generation of a milling signal can also include the generation of a representative instruction signal for moving the platform to a desired location.
Thus, the invention provides apparatus and methods that employ a focused particle beam system to mill a second structural element without irradiating a sensitive first structural element, e.g., a read head, of a recording transducer. In this manner, the focused particle beam system produces a desired pole-tip configuration. By producing a desired pole-tip configuration, the system produces an improved recording transducer capable of higher storage density than recording transducers made according to prior art techniques. Further, the system uses existing features of a multi-layer device that forms a recording transducer. A focused particle beam for practice of the invention can include an ion beam. electron beam, x-ray beam, optical beam or other similar source of directable radiant energy.
These and other features of the invention are more fully set forth with reference to the following detailed description, and the accompanying drawings.